Electric circuit breakers

ABSTRACT

An apparatus for improving the assembly and operation of an electric circuit breaker is disclosed wherein pivotally mounted contact arm assemblies and a releasable trip lever, retained by a current-responsive latch system are interconnected by a toggle linkage and springs to a manually movable handle operable to collapse and straighten the toggle to effect opening and closing movement, respectively, of the contact arm assemblies. The toggle linkage and movable handle are constructed in such a manner that the toggle tension springs will maintain the handle in the ON or closed circuit position without the aid of auxiliary devices whenever the circuit breaker contacts are welded closed regardless of whether the circuit breaker operating mechanism is latched or unlatched. To facilitate assembly and improve operation, one movable contact arm assembly is welded to the operating shaft and the remaining contact arm assemblies are mechanically fastened thereto and thereafter the subassembly is releasably journaled to stationary mounting brackets with fork-like retainer clips. Adjustable backup springs ensure maximum operating contact pressure of the contact arm assemblies on mating stationary contacts and minimize contact bounce and blow-open. A heat sink dissipates heat caused by overload currents within the circuit breaker and thereby prevents damage to the current-responsive elements. A counter weight attached to the trip lever prevents false release of the lever and opening of the breaker contacts due to external mechanical shocks and vibrations experienced by the breaker.

United States Patent [1 1 Link et al.

[4 1 Nov. 19, 1974 1 ELECTRIC CIRCUIT BREAKERS [75] Inventors: Donald A. Link, Hubertus; Fred 11.

Williams, Oshkosh, both of Wis.

[73] Assignee: Cutler-Hammer, Inc., Milwaukee,

Wis.

[22] Filed: Feb. 6, 1973 [21] Appl. No.: 330,031

[52] US. Cl 337/59, 200/153 G, 337/56 [51] Int. Cl. H0lh 71/16 [58] Field of Search 337/58, 59, 46, 47, 48, 337/49, 52, 55, 56, 53, 345; 200/153 0 [56] References Cited UNITED STATES PATENTS 3,422,381 l/l969 Toth 337/46 3,510,818 5/1970 Myers 337/55 3,621,189 11/1971 Link et al7 l 337/57 3,760,308 9/1973 Misencik ct a1. 337/46 Primary Examiner-Arthur T. Grimley Attorney, Agent, or Firm-H. R. Rather; Wm. A. Autio latch system are interconnected by a toggle linkage and springs to a manually movable handle operable to collapse and straighten the toggle to effect opening and closing movement, respectively, of the contact arm assemblies.

The toggle linkage and movable handle are constructed in such a manner that the toggle tension springs will maintain the handle in the ON or closed circuit position without the aid of auxiliary devices whenever the circuit breaker contacts are welded closed regardless of whether the circuit breaker operating mechanism is latched or unlatched.

To facilitate assembly and improve operation, one movable contact arm assembly is welded to the operating shaft and the remaining contact arm assemblies are mechanically fastened thereto and thereafter the subassembly is releasably journaled to stationary mounting brackets with fork-like retainer clips. Adjustable backup springs ensure maximum operating contact pressure of the contact arm assemblies on mating stationary contacts and minimize contact bounce and blow-open. A heat sink dissipates heat caused by overload currents within the circuit breaker and thereby prevents damage to the current-responsive elements. A counter weight attached to the trip lever prevents false release of the lever and opening of the breaker contacts due to external mechanical shocks and vibrations experienced by the breaker.

11 Claims, 13 Drawing Figures ELECTRIC CIRCUIT BREAKERS BACKGROUND OF THE INVENTION -l. Field of the Invention This invention generally relates to electric circuit breakers and more particularly to unique improvements relating to the assembly and operation of component parts therein.

2. Description of the Prior Art A wide variety of devices have heretofore been provided for improving the assembly and operation of electric circuit breakers. Although such devices have generally served their purpose, no single device has proven entirely satisfactory from an assembly and operational standpoint.

For example, in some circuit breakers, it is possible to manually move the operating handle between ON and OFF positions even though the breaker's movable contacts are welded in closed circuit position to their mating stationary contacts. In such breakers the handle sometimes will remain in the OFF position after having been moved to such position particularly when the handle is connected to a tension spring to an overcenter toggle linkage of an operating mechanism which is in a latched" position. In such a situation, where the handle falsely indicates OFF, a workman may proceed to work on a device connected thereto under the false impression that line power is disconnected and may be injured as a result thereof. To avoid the occurrence of FALSE-OFF indication, mechanical devices have been proposed which spring bias the handle to read ON under contact welded conditions. To ensure operativeness these devices require the latch mechanism bemaintained in the unlatched mode. These devices accomplish unlatching by utilizing mechanical linkage to trip the operating mechanism upon handle movement towards the OFF position thereby permitting the toggle spring to bias the handle back to ON. In cases where the mechanism is already tripped the handle is biased to read ON by the toggle spring and any attempt to reset the latch mechanism is prevented by mechanical linkage which disables the latch mechanism and will bias the handle to read ON. A further approach for preventing FALSE-OFF indication provides for mechanically blocking the handle so it cannot be pulled to the OFF position whenever the contacts are welded. While these devices have generally served their purpose, they provide no protection in the event of their malfunctioning. Consequently, such devices do not provide 100 percent assurance that the circuit will be open when the circuit breaker handle so indicates.

Also in multipole circuit breakers, the center pole contact assembly is normally fastened with clamps to an operating shaft common with the outer poles and must, in addition to transmitting its own contact presassembly either to or from a common mounting bracket which also carries the pivot points of cooperating mechanism within the breaker housing. Instead shafts are normally individually inserted and journaled directly to the circuit breaker casing rather than the pivot support for cooperating mechanisms or are journaled in separate support members which are attached to the molded case of the circuit breaker. Such means of joumaling the operating shaft does not lend itself to precise alignment with pivot points of cooperating component parts nor to subassembly techniques for circuit breaker components.

Moreover, circuit breakers of current design are generally susceptible to contact bounce. Whenever movable contacts are closed, they normally bounce open a period of time and generate an are each time they contact the stationary contacts. In some instances, this arcing causes the contacts to weld thereby preventing the circuit breaker from operating as intended to open the contacts in response to current overloads.

Furthermore, current-responsive elements of existing circuit breakers sometimes become damaged from excessive heat during interruption of certain levels of overload currents such as those just below that required to magnetically trip the circuit breaker. Such heat causes the current-responsive elements to deflect or rupture thereby preventing the circuit breaker from operating as intended.

Still further, some circuit breakers are extremely sensitive to external mechanical shocks and vibrations which cause the circuit breaker mechanism to become unlatched and thereby cause the contacts to open when such sensitivity is reached regardless of the current load. Such false tripping and opening of the breaker contacts is undesirable from an operational standpoint.

SUMMARY OF THE INVENTION The general object of the invention is to provide an improved circuit breaker which circumvents the problems heretofore noted as well as other disadvantages of the prior art.

More specifically it is an object of the present invention to generally improve the details of construction and assembly of parts for circuit breakers and their operational characteristics when in use.

It is a specific object of this invention to provide a collapsing-toggle-operating mechanism for an electric circuit breaker having an improved arrangement for preventing false OFF indication when the circuit breaker contacts are welded closed irrespective of the latching position of the breaker.

It is a specific object of this invention to provide an improved method of rigidly fastening movable contact assemblies to an operating shaft to prevent relative motion therebetween.

It is a specific object of this invention to provide an improved method of releasably joumaling the shaft'and contact subassembly to mounting brackets carrying pivot points of cooperating component parts to assure precise coordination therebetween.

It is a specific object of this invention to provide a contact arm assembly for an electric circuit breaker having an improved spring arrangement for preventing rebound and blow-open" of the movable contact arm and for improving contact pressure to maintain mating contacts in closed circuit position.

It is a specific object of this invention to provide a current-responsive device for an electric circuit breaker having an improved means for absorbing heat caused by current overloads to prevent damage to the current-responsive elements.

It is a specific object of this invention to provide a balanced trip lever for an electric circuit breaker for preventing false tripping thereof in response to external mechanical shocks and vibrations experienced by the circuit breaker.

These and other objects and advantages of the invention will become more apparent in the following specification and claims when read in conjunction with the following drawings.

DETAILED DESCRIPTION OF THE DRAWINGS In describing the present invention, reference will be made to the accompanying drawings forming a part of the instant disclosure wherein:

FIG. I is a side elevational view partially in cross section of an electrical circuit breaker in the ON position exposing internal parts subject of the present invention.

FIG. 2 is a plan view of the circuit breaker shown in FIG. 1 taken along line 22.

FIG. 3 is a fragmentary side elevation view, partially in cross section, illustrating the electric circuit breaker in FIG. I in the OFF or open circuit position.

FIG. 4 is a fragmentary side elevation view, partially in cross section, illustrating the electrical circuit breaker in FIG. 1 in the TRIP position.

FIG. 5 is a side elevation view partially in cross section illustrating the electrical circuit breaker in FIG. 1 with the operating handle manually position towards OFF with the contacts welded in the closed circuit position and further illustrating the spring bias of the operating handle towards the ON position with the mechanism latched.

FIG. 6 is a side elevation view partially in cross section illustrating the electrical circuit breaker in FIG. 1 with the operating handle manually biased towards OFF with the contacts welded in closed circuit position and further illustrating the spring bias of the operating handle towards the ON position with the mechanism unlatched.

FIG. 7 is a side elevation view partially in cross section of a contact assembly and operating shaft constructed in accordance with the instant invention.

FIG. 8 is a fragmentary view, partially in cross section, illustrating another contact arm assembly constructed in accordance with the instant invention.

FIG. 9 is a side elevation view partially broken away of a mounting bracket and retainer clip constructed in accordance with the instant invention.

FIG. I0 is a side elevation view of the devices in FIGS. 7 and 9 illustrating the assembly of the operating shaft and contact arm subassembly to the mounting brackets in accordance with the instant invention.

FIG. 11 is a fragmentary front elevation view, broken away and partially in cross section, taken along line llll of FIG. of the retainer clip of the instant invention.

FIG. 12 is a perspective view of a pressure plate constructed in accordance with the instant invention.

FIG. 13 is a plan view, partially broken away and in cross section of the pressure plate along line I3-l3 of FIG. I.

DETAILED DESCRIPTION OF THE INVENTION A conventional circuit breaker adaptable for use with the instant invention is fully described in US. Pat. No. 3,621,189 granted to Donald A. Link et al. on Nov. 16. 1971. the disclosure of which patent is incorporated herein by reference and set forth in the following.

With reference in more detail to FIGS. 1 and 2 ofthe drawings. there is shown an electric circuit breaker I generally referred to as being of molded case construction wherein the breaker mechanism is housed within a molded insulating housing or case 2 and cover 4 secured together by conventional means such as screws. rivets or the like (not shown). The circuit breaker may be a single or multipole device. the individual poles each having a line terminal and contact plate assembly 6, a stationary contact 8, a movable contact 10, a pivotally supported contact carrier or arm 12 and a load terminal and plate assembly I4. Each pole is further provided with current-sensing means 16 olthe thermal and magnetic type for a dual-sensing system. operable upon an overload condition to move a common trip bar 18 extending across all the poles.

Each contact arm 12 is pivotally carried between the sides of individual frames 20 which in turn are separately secured to a common insulated shaft assembly 22 which extends across all the poles of the breaker. The shaft assembly 22 is rotatably supported in a pair of spaced mounting brackets 24 secured upon the floor of molded case 2. A tension spring 25 is disposed between the frame 20 and contact arm 12 in the area opposite contact 10 as shown in FIG. I to provide contact pressure for maintaining the breaker contacts closed.

An operating mechanism 26 for the circuit breaker is shown in FIG. 3 located in one pole of the breaker to drive that particular movable contact assembly and the common shaft 22 which drives the contact assemblies of the remaining poles. In the breaker shown in the drawings, the operating mechanism 26 includes a latch lever 27 mounted on a pivot pin 28 secured between the mounting brackets 24 near their upper ends. A pair of parallel upper toggle links 30 are pivotally attached to the latch lever 27 by a pivot pin 32 to depend from the latch lever 27. A pair of parallel lower toggle links 34 are pivotally attached to the opposite sides of the frame 20 -of the pole containing the operating mechanism by a pivot pin 36 to extend upwardly from the frame toward the depending ends of links 30. A knee pin 38 provides a common pivotal connection for the adjacent ends of the upper and lower toggle links 30 and 34, respectively.

The operating mechanism 26 further includes an operating lever 40 which overlies the linkage and mounting brackets 24 and has depending side legs which are pivotally supported on the external sides of mounting brackets 24. A pair of helical tension springs 42 are connected between the knee pin' 38 and the upper portion of the operating lever 40 which spans the side links. A molded insulating handle 44 is cooperatively shaped to rest upon the operating lever 40 and be maintained in position thereon by engagement with the inner portion of cover 4. Handle 44 projects externally of the enclosing case through an elongated opening 46 in cover 4 to permit manual movement of the operating lever 40.

The circuit breaker is further provided with a doubleacting latch system operable to restrain the otherwise free end of latch lever 27. The latch system includes a primary latch 48 pivotally mounted between the brackets 24 on a pin 50 fixed at its ends to the brackets. Latch 48 has an upstanding leg 52 thereon which is provided with an opening for receiving the end of latch lever 27 and a depending leg 54 having a stepped lower edge to provide a latching surface between the stepped levels. A torsion spring 56 is disposed around pin 50 to engage latch 48 and one bracket 24 at its ends, thereby providing a counterclockwise bias for the latch.

A secondary latch member 58 is also pivotally mounted between the mounting brackets 24 on a pin 60 fixed to the bracket. Secondary latch 58 has a horizontally projecting L-shaped leg 62 which engages the stepped surface on depending leg 54 of latch 48 to restrain the latter against the combined actions of the counterclockwise bias of torsion spring 56 and the urging of the latch lever 27. Secondary latch member 58 is also provided with a torsion spring 64 disposed around pin 60 and is connected between the latch 58 and one of the mounting brackets 24 to bias the secondary latch 58 counterclockwise, thereby urging leg 62 against the stepped edge of lower leg 54 on latch 48. A leg 66 is also formed on secondary latch 58 to project upwardly at substantially right angles with the leg 62 thereon. Common trip bar 18 is secured to the leg 66 at its upper end. the trip bar 18 extending transversely of the breaker housing whereby the current-sensing means 16 of each pole of the breaker may engage the bar 18 to actuate the latching system.

The circuit breaker is shown in the contact closed position in FIG. I. Latch 48 of the latching system restrains latch lever 27 in a fixed position to thereby fixedly locate the uppermost pivot pin 32 of the toggle linkage. Handle 44 is moved to the right hand end of operating 46 in cover 4 to pivot the operating lever 40 in a clockwise direction. The latter movement carries the upper ends of springs 42 overcenter of the pivot pin 32 which then act upon the knee pin 38 to cause it to move to the right and straighten the linkage. Movement of the knee pin to the right is limited by engagement of the upper toggle links 30 with portions 68 of the mounting brackets 24. The straightening action of the linkage drives the lower pivot pin 36 downward to pivot frame 20 and common shaft 22 in a clockwise direction thereby causing downward motion of the contact arms 12 of all the poles to affect closing of the movable contacts upon the stationary contacts 8.

Opening of the contacts is accomplished manually by moving handle 44 to the left-hand end of the opening 46 to return the line of action of springs 42 overcenter of the pivot pin 32 to the original position as shown in FIG. 3. The springs 42 act upon knee pin 38 to move it to the left, thereby causing the linkage to collapse which raises the lower pivot pin 36 and pivots the frame 20, shaft assembly 22 and contact arm 12 counterclockwise to separate the contacts 8 and It). The counterclockwise movement of frame is limited by engagement thereof with portions 68 of the mounting brackets 24.

Opening of the contacts automatically in response to an overcurrent condition is accomplished by means of the latching system in cooperation with-the currentsensing means as shown in FIG. 4. Excessive ctirrent in the isolated circuit path of any pole of the breaker is sensed by the overcurrent sensing means 16 of that particular pole. Sensing means 16 moves against common trip bar 18 in response to an overcurrent condition to pivot the secondary latch member 58 clockwise. thereby releasing the primary latch 48 which in turn is moved counterclockwise by virtue of the combined actions of spring 56 and the urging of latch lever 27 to affect release of the latter. When released. the latch lever 27 moves in a clockwise direction about pivot pin 28 due to the influence of springs 42 acting through upper toggle links 30 and in so doing carries the upper pivot pin 32 of the toggle linkage overcenter ofthe line ofaction of the spring 42 to collapse the linkage and open the contacts.

Having generally described the overall arrangement and operation of a known electric circuit breaker. the unique improvements relating to the assembly and operation of such a circuit breaker will now be described in detail.

Referring now to FIG. 5, contacts 8 and 110 are shown welded together in closed circuit relationship with handle 44 physically moved to the OFF or RESET position and the operating mechanism shown "latchedf- Under such condition. some prior art devices will continue to indicate OFF upon release of handle 44 even though the contacts are closed. To circumvent this problem. operating devices have been proposed which unlatch the operating mechanism and thus bias the handle to the ON position. Other devices lock the handle in the ON position barring movement to OFF in the first instance whenever contacts are welded. As can readily be seen, these devices depend upon additional operating mechanisms to those normally required to perform the circuit breaking function. Such mechanisms are subject to failure and consequently do not provide complete assurance that the breaker handle will indicate ON when the contacts are welded.

The instant invention assures that whenever contacts 8 and 10 are welded in the closed position, handle 44 of electric circuit breaker I will always indicate ON or return to that position after having been manually moved to the OFF or RESET position or any other position intermediate thereof regardless of whether the operating mechanism 26 is latched or unlatched as shown in FIGS. 5 and 6 without the need for auxiliary devices such as those mentioned above. This is achieved by positioning the respective pivot locations of the handle pivot boss 69. knee pin 38 and pins 32 and 36 of the upper and lower toggle links 30 and 34 as shown in FIGS. 5 and 6. It should be noted with such an arrangement that for any handle position. the location of linkage pins 32, 36 and knee pin 38 is always to the right of the handle pivot pin 69, and consequently. the handle 44 will always be biased by the operating springs 42 toward the ON position regardless of whether or not the latch lever 27 of the operating mechanism 26 is latched or unlatched.

Referring now to FIG. 7, there is shown therein a movable contact assembly of a multipole circuit breaker fixedly attached to the insulated shaft assembly 22 which laterally extends across and carries all poles of the breaker. Center pole frame 20 shown therein is welded to the shaft 22 at point where the shaft 22 passes therethrough. A stiff backup or helper spring 73 (discussed later hereinafter) is also welded to frame 20 and shaft 22 at points 74 and 75, to form a rigid subassembly for subsequent insertion thereof into mounting brackets 24. Such means of fastening eliminates a potential source of free motion between the operating mechanism 26, shaft 22 and contact arm 12. Existing breakers utilize screws and clamping arrangements which tend to loosen or permit deflection between the pole assemblies causing loss of force transmittal through the toggles to the movable contact assemblies.

Each of the outer pole frames 20 are shown firmly secured as shown in FIG. 8 to an insulated portion 76 of the shaft 22 by a retaining clip 77 and screw 78. Clip 77 is inserted as shown in FIG. 8 at one end through an opening 79 in the frame 20 and a reinforcing pressure plate 80. Screw 78 is received through an opening 81 in the pressure plate 80 and frame 20 to a tapped hole in the opposite end of clip 77 to draw clip 77 about the insulated portion 76 of the shaft 22 by taking up space 82 shown therein. It should be noted that the clip 77 and screw 78 utilized as shown in FIG. 8 provide a very rigid mechanical connection of the individual frames 20 to the shaft 22 showing no tendency to permit free motion or deflection between the operating mechanism 26 and contact arms 12 as is experienced with existing fastening mechanical devices.

A stiff backup or helper spring 90, like spring 73, is formed as shown in FIG. 8 to bear against arm 12 for applying additional contact pressure thereto. Spring 90 is secured to the frame 20 at one extreme end by the bearing action of the shoulder 84 thereon as space 82 is taken up and by the weldment at point 92 to the frame 20 intermediate its other end. It should be noted that the opening 94 between springs 73 and 90 and contact arms 12 results whenever the contacts 8 and are in the open circuit position. Both springs 73 and 90 are advanced this distance to contact and bear on the backside of anns 12 just prior to final in-line position of the toggle linkage when the operating handle 44 is moved into the closed circuit position shown in FIG. 1. At this, point the mechanical advantage of the toggle linkage generates a large force through the operating mechanism 26, frame and springs 73 and 90 to arms 12. The low deflection characteristics of the stiff springs ensures such force is transmitted to arms 12 to minimize contact separation resulting from contact rebound and blowing open when the breaker experiences high current overloads or short circuits.

Retainer 98 shown in FIGS. 911 is utilized to releasably secure and journal the bearing portion 100 of the shaft 22 and subassemblies shown in FIGS. 7 and 8 to the mounting brackets 24. Ears 101, 102 and 103 of retainer 98 slidably engage surface 104 of brackets 24 during insertion. The ears 101, 102 and 103 are adjusted to obtain sufficient frictional engagement with surface 104 of the brackets 24 to ensure retainer 98 will remain in place prior to placing the mounting brackets 24 and subassembly in the molded case 2. Thereafter shoulder 106 of case 2 shown in FIG. 11 abuts against retainer 98 and prevents its movement or release from the brackets 24.

As can readily be seen, use of such a retainer permits rapid assembly and disassembly of the subassembly to the brackets 24 in proper alignment with cooperating parts. It can also be seen such retaining feature permits placement of all pivot points of cooperating parts on a common mounting bracket 24 as is shown in FIG. 10, thereby obviating misalignment problems experienced by existing circuit breakers wherein operating shafts are normally journaled in support members attached to the molded case or otherwise supported independently of the operating mechanism pivot points within the mounting brackets 24. Common location of all pivot points within the mounting brackets 24 also eliminates the need for fine adjustments during the assembly stage to assure proper alignment of the various component parts within the breaker which in operation depend on one another.

Another feature of the instant invention provides for a heat storage device such as a heat sink 110 rigidly attached to heater 112 to dissipate and store excessive heat from both the heater 112 and bimetal element 114 of means 16 caused by overload currents within the circuit breaker. Heat sink 110 is constructed of a good heat conducting material such as copper and is welded at the hot spot or normal rupture point of the heater as shown in FIG. 3. Bimetal element 114 is riveted to heater 112 in heat conducting relationship therewith as shown in FIG. 3. The provision of the heat sink 110 prevents deflection and rupturing of the heater 112 and deflection of the associated bimetal element 114 attached thereto. Such rupturing destroys the heater and such deflection is undesirable in that trip calibration between means 16 and trip bar 18 is disturbed causing the circuit breaker to malfunction.

An additional feature of the present invention provides for a counterweight attached by conventional fastening devices (not shown) to the lower portion of leg 66 of the circuit breaker tripping mechanism to prevent false tripping thereof in response to external mechanical shocks or vibrations. The counter weight 120 is selected and positioned to balance the inertial forces experienced by leg 66 about the pin 60 caused by the uneven distribution of mass pivoting thereabout. As can be seen in FIG. 3, external mechanical shocks or vibrations will have no significant net effect upon leg 66 to cause release of latching parts and opening of the contacts 8 and 10 when such counterweight is properly positioned.

A pressure plate shown in FIG. 12 is a further feature of the present invention for assuring that the heater 112 and current-sensing means 16 is firmly seated within the molded insulated case 2 to obtain a fixed trip calibration between means 16 and trip lever 18. The pressure plate 130 is constructed of a resilient material such as metal plate and is notched and formed with tabs 132 and 134 as shown in FIG. 12 of the drawings. The tabs assume a spread posture in their relaxed position, and upon insertion into the case 2, firmly spring and seat the heater 112 and current-sensing means 16 therein in tripping relationship with trip bar 18 by bearing against the heater 112 and insulating material 136 as shown in FIG. 13.

As is evident from the foregoing description and drawings, the present invention provides substantial improvements in the operation and assembly of electric circuit breakers. It will also be apparent that various details of the illustrated forms of the present invention may be varied without departing from the inventive concept. It will accordingly be understood that it is intended to embrace within the scope of this invention such modifications as may be embraced by the skill of the art.

We claim:

1. In an electric circuit breaker. the combination with an insulating housing, stationary contact meansin said housing, movable contact means and an operating mechanism in said housing for said movable contact means including an operating handle pivotally movable between ON and OFF positions, latch means movable between latched and unlatched positions. collapsible toggle linkage connected to said latch means and spring means connected between said latch means and said toggle linkage and movable by said handle over center of said linkage to actuate the latter between essentially collapsed and straightened positions to effect operation of said movable contact means between open and contact engaged positions with said stationary contact means, of second spring means normally out of engagement with said movable contact means and means responsive to movement of said toggle linkage to transmit the large operating force developed by said toggle linkage when it assumes a generally in-line position to said second spring means to provide corresponding contact closing force between said movable and stationary contact means.

2. An electric circuit breaker according to claim 1 wherein said movable contact means includes a contact carrier and a frame connected thereto and wherein said second spring means is connected to said frame and operable to engage said contact carrier and transmit the linkage operating force thereto just prior to said linkage assuminga generally in-line position,

3. An electric circuit breaker according to claim 1 wherein said .breaker further includes an operating shaft responsive to said handle and connected to said movable contact means, wherein said breaker further includes a mounting bracket mounted in said housing having a bearing surface to receive said operating shaft, and wherein said breaker further includes a removable retainer means mountable on said mounting bracket to retain and journal said operating shaft on the bearing surface of said mounting bracket.

4. An electric circuit breaker according to claim 1 wherein said circuit breaker includes current responsive means operable to cause unlatching of said latch means to cause movement of said movable contacts into open circuit position in response to current overloads, said circuit breaker further including therein heat storage means operative to remove and store heat from said current responsive means caused by such overloads to prevent deflection or rupture thereof and subsequent loss of trip calibration with said latch means.

5. An electric circuit breaker according to claim 1 wherein said latch means includes a pivotally mounted latch member responsive to said current responsive means to unlatch said latch means to cause opening of the circuit between said contacts and wherein said latch means further includes a counterweight means attachable to said pivotally mounted latch member to balance the inertial forces of mass about the pivot point of said member to ensure said member is not tripped by external vibration or shock to said circuit breaker.

6. An electric circuit breaker according to claim 1 wherein said circuit breaker further includes pressure plate means supportable within said housing and operable with said housing to position said currentresponsive means thereagainst as a reference point for setting trip calibration between said current-responsive and said latch means.

7. An electric circuit breaker comprising, in combination:

an insulating housing; stationary contact means mounted in said housing; movable contact means movable into and out of closed circuit with said stationary contact means;

an operating shaft mounted within said housing sup porting said movable contact means;

an operating mechanism within said housing operable to move said movable contact means relative to said stationary contact means;

a mounting bracket in said housing having partial bearing surfaces to receive said operating shaft; and

removable retainer means mountable on said mounting bracket to complete the bearing surfaces for and retain and journal said operating shaft on the bearing surfaces of said mounting bracket.

8. An electric circuit breaker according to claim 7 wherein said operating mechanism includes a collapsible toggle linkage for operating one of said movable contacts and wherein said breaker further includes means responsive to said operating mechanism for initially biasing said movable contact means into contact with said stationary contact means spring means responsive to movement of said toggle linkage and operable totransmit the operating force of said linkage to said movable contact means when said toggle linkage assumes a generally in-line position thereby utilizing the large force generated at the end of the linkage movement to provide final contact closing pressure to said movable and stationary contact means.

9. An electric circuit breaker according to claim 7 wherein said stationary and movable contact means comprise a plurality of mating stationary and movable contacts and wherein one of said movable contacts is integral with said operating shaft.

10. An electric circuit breaker comprising in combination:

an insulating housing;

stationary contact means mounted within said housing movable contact means movable into and out of closed circuit with said stationary contacts;

an operating mechanism within said housing including a collapsible toggle linkage for operating said movable contact means; and

means including spring means normally out of engagement with said movable contact means and responsive to movement of said toggle linkage to transmit the operating force of said linkage to said movable contact means when said linkage assumes a generally in-line position thereby utilizing the large force generated at the end of the linkage movement to provide final contact closing pressure between said movable and stationary contact means.

11. An electric circuit breaker according to claim 10 wherein said movable contact means includes a frame and attached contact carrier and wherein said spring means is mounted on said frame and is operable to engage said carrier in line with said movable contact means and transmit the toggle linkage operating force in-line position. 

1. In an electric circuit breaker, the combination with an insulating housing, stationary contact means in said housing, movable contact means and an operating mechanism in said housing for said movable contact means including an operating handle pivotally movable between ON and OFF positions, latch means movable between latched and unlatched positions, collapsible toggle linkage connected to said latch means and spring means connected between said latch means and said toggle linkage and movable by said handle over center of said linkage to actuate the latter between essentially collapsed and straightened positions to effect operation of said movable contact means between open and contact engaged positions with said stationary contact means, of second spring means normally out of engagement with said movable contact means and means responsive to movement of said toggle linkage to transmit the large operating force developed by said toggle linkage when it assumes a generally in-line position to said second spring means to provide corresponding contact closing force between said movable and stationary contact means.
 2. An electric circuit breaker according to claim 1 wherein said movable contact means includes a contact carrier and a frame connected thereto and wherein said second spring means is connected to said frame and operable to engage said contact carrier and transmit the linkage operating force thereto just prior to said linkage assuming a generally in-line position.
 3. An electric circuit breaker according to claim 1 wherein said breaker further includes an operating shaft responsive to said handle and connected to said movable contact means, wherein said breaker further includes a mounting bracket mounted in said housing having a bearing surface to receive said operating shaft, and wherein said breaker further includes a removable retainer means mountable on said mounting bracket to retain and journal said operating shaft on the bearing surface of said mounting bracket.
 4. An electric circuit breaker according to claim 1 wherein said circuit breaker includes current responsive means operable to cause unlatching of said latch means to cause movement of said movable contacts into open circuit position in response to current overloads, said circuit breaker further including therein heat storage means operative to remove and store heat from said current responsive means caused by such overloads to prevent deflection or rupture thereof and subsequent loss of trip calibration with said latch means.
 5. An electric circuit breaker according to claim 1 wherein said latch means includes a pivotally mounted latch member responsive to said current responsive means to unlatch said latCh means to cause opening of the circuit between said contacts and wherein said latch means further includes a counterweight means attachable to said pivotally mounted latch member to balance the inertial forces of mass about the pivot point of said member to ensure said member is not tripped by external vibration or shock to said circuit breaker.
 6. An electric circuit breaker according to claim 1 wherein said circuit breaker further includes pressure plate means supportable within said housing and operable with said housing to position said current-responsive means thereagainst as a reference point for setting trip calibration between said current-responsive and said latch means.
 7. An electric circuit breaker comprising, in combination: an insulating housing; stationary contact means mounted in said housing; movable contact means movable into and out of closed circuit with said stationary contact means; an operating shaft mounted within said housing supporting said movable contact means; an operating mechanism within said housing operable to move said movable contact means relative to said stationary contact means; a mounting bracket in said housing having partial bearing surfaces to receive said operating shaft; and removable retainer means mountable on said mounting bracket to complete the bearing surfaces for and retain and journal said operating shaft on the bearing surfaces of said mounting bracket.
 8. An electric circuit breaker according to claim 7 wherein said operating mechanism includes a collapsible toggle linkage for operating one of said movable contacts and wherein said breaker further includes means responsive to said operating mechanism for initially biasing said movable contact means into contact with said stationary contact means spring means responsive to movement of said toggle linkage and operable to transmit the operating force of said linkage to said movable contact means when said toggle linkage assumes a generally in-line position thereby utilizing the large force generated at the end of the linkage movement to provide final contact closing pressure to said movable and stationary contact means.
 9. An electric circuit breaker according to claim 7 wherein said stationary and movable contact means comprise a plurality of mating stationary and movable contacts and wherein one of said movable contacts is integral with said operating shaft.
 10. An electric circuit breaker comprising in combination: an insulating housing; stationary contact means mounted within said housing movable contact means movable into and out of closed circuit with said stationary contacts; an operating mechanism within said housing including a collapsible toggle linkage for operating said movable contact means; and means including spring means normally out of engagement with said movable contact means and responsive to movement of said toggle linkage to transmit the operating force of said linkage to said movable contact means when said linkage assumes a generally in-line position thereby utilizing the large force generated at the end of the linkage movement to provide final contact closing pressure between said movable and stationary contact means.
 11. An electric circuit breaker according to claim 10 wherein said movable contact means includes a frame and attached contact carrier and wherein said spring means is mounted on said frame and is operable to engage said carrier in line with said movable contact means and transmit the toggle linkage operating force thereto just prior to said linkage assuming a generally in-line position. 